A junction box which functions as a general power shut-off unit is provided in a power-source circuit of a battery. The junction box includes electronic components such as a relay(s) and a fuse(s) which conduct opening and closing (shut-off) of the power-source circuit and which distribute power among accessory components of a vehicle.
Patent Literature 1 discloses one example of the junction box. In this technique, when the electronic component has failed, only the electronic component can be checked and replaced easily, inexpensively and quickly in the course of using a battery.
In the case of the junction box disclosed in the Patent Literature 1, various electronic components and a relay for shutting off a power circuit are integrated with each other and are fastened to a battery frame. In this example, the plurality of electronic components are fixed to an inside of the junction box, and the relay is fixed to an upper surface of the junction box. This junction box itself is fixed to a lower case of the battery.
In an electric vehicle and the like, a large-size relay is used to deal with high voltages. In the technique disclosed in the Patent Literature 1, the relay having a heavy weight is provided on the upper surface of the junction box. Hence, there is a risk that a plate portion of the junction box on which the relay is mounted sags or bends resulting in rupture or breakage thereof due to a running vibration or the like of the vehicle. Therefore, it is necessary to thicken the plate portion in order to strengthen this plate portion. Accordingly, an unfavorable weight increase is caused.